Rail flaw detector mechanism



Nov. 23, 1937. w. M. PERRY 2,099,823

RAIL FLAW DETECTOR MECHANISM Filed May 20, 1936 IN VEN TOR Walter M. Perry A TTORNEYS.

Cal

Patented Nov. 23, 1937 UNITED STATES RAIL FLAW DETECTOR MECHANISM Walter M. Perry, Brooklyn, N. Y., assignor to Sperry Products, Inc., Brooklyn, N,'Y., a cor-' notation of New York Application May 20, 1936, Serial No. 80,747

4 Claims. (Cl. 175183) This invention relates to rail fissure detector mechanism of the type employed on the Sperry rail fissure detector cars. These mechanisms operate upon the principle of .passing current through the rail to establish an electromagnetic field surrounding the same and exploring the said field with flux-responsive means, such as induction coils,.for the purpose of detecting any irregularities due to the presence of internal fissures.-

It has been found, however, that the electromagnetic field surrounding the rail is distorted by thenetic pole. Such pole distorts'the electromagnetic field and is frequently picked up in the same manner as an internal defect. Also, it sometimes happens that surface defects, such as burns on the surface of the railhead, serve to set up local magnetic fields which also are sometimes picked up by the detector mechanism in thesame manner as an internal defect. Such actuation of the detector mechanism by surface poles due either to poor contact of the current brushes or to the presence of surface defects such as burns, is undesirable in thatit confuses the record and not only slows up the detection operation but frequently causes inaccuracy due to misinterpretation of the record because actual internal defects are mistaken for surface defects.

It is the principal object of my invention, therefore, to provide a mechanism wherein the undesirable effects of factors other than internal defects will be eliminated.

Other objects and advantages of this invention will become apparent in the following detailed description thereof:

In the accompanying drawing,

Fig. 1 is a side elevation of a portion of a Sperry rail fissure detector mechanism showing one form of my invention applied thereto.

Fig. 2 is a detail showing a modified form of the invention disclosed in Fig. 1.

Fig. 3 is an end view of still another form of my invention.

Referring to Fig. 1 of the drawing, there is disclosed a portion of a Sperry rail fissure detector car which includes a car-body I supported on the rail by wheels, not shown, and having suspended therefrom the rail fissure detector mech-' anism. Said mechanism maybe supported ona carriage ll having flanged wheels I2 whereby it is adapted to ride upon the rail R, the said car-'- riage being normally held in elevated position by means such as cables l3 and springs, not shown, but a'dapted to be lowered into operating-position in el'i'gagement with the rail by means of 'fiuid' pressure supplied to cylinders l5 to force pistons l6 downwardly against the action of the retractile springs. When the carriage I l is in-operating position in engagement with the rail, it'is adapted to supply current to the rail R from a generator G mounted withinthecar-body l0 and supplying current to spaced sets of brushes i1 and I8 to set up an electromagnetic field surnumber of lines of force,- but on entering a region of flaw, first one and then the other of the coils will cuta different number of lines of force to generate a differential E. M. F. which after being suitably amplified may be caused to operate any suitable indicator'such as a recorder. The coils 20 are supported at a constant distance above the railhead within a housing 2| which isfixed upon a carriage 22 adapted to ride on the-rail by means such as sets of wheels 23. The said carriage is supported from the current brush carriage H by means such as bolts 24 extending loosely through a bracket 25 fixed to the said car riage. ll, said bolts being held in position by means of nuts 21 and springs 26. By this con-' struction the carriage'22 is given a movement independent of the movements of the current brush carriage ll so that the said detector carriage 22 may at all times follow the contour of the rail surface to maintain the housing 2| and hence the axes of coils 20 always at a fixed distance above the rail surface.

In order that the molecules may be homogeneously aligned by the time the detector coils pass over any given point of the rail, it has been found desirable to premagnetize the rail by means of an additional set of brushes positioned in advance of the brushes l1 and supplied with current from an auxiliary generator G within the car-body II), or from an additional winding on the generator G. An auxiliary circuit from brushes 30 through brushes I1 is thus established in ad- Vince of and in the same direction as the circuit from brushes II to brushes i8, and thus preenergllstion is effected to properly align the molecules, which has been found to result in the coils ll operating more emc'iently to detect a greater number of internal defects.

If any of the cluster of brushes constituting the set II or the brushes constituting the set II should lose contact or make poor contact with the rail surface. it has been found that there is formed a local magnetic pole which sometimes affects the coils II in the same manner as an internal defect and is indicated by the indicating mechanhm in the same manner as an internal defect. Such local magnetic effects are set up not only by reason of poor contact between current brushes and the rail sin'face, but also by certain dirt spots which have been ground into the rail surface and also by surface burns caused by slipping of locomotive wheels, or the like. These local magnetic disturbances which affect the pick-up coils II are undesirable because they result in a multiplicity of false indications, which makes operation more diflicult as well as slower and less accurate. In order to eliminate the effect of magnetic poles formed in the surface of the 'railhead, 1- pro--.

vide the following mechanisms which I have found to be efficient. One such mechanism is disclosed in Fig. 1 and consists in mounting, referably between the. current brushes i1 and the detector carriage 22, a magnetic conductor by-pass ll which may take the form of a block of steel maintained either in contact with the rail surface or preferably slightly out of contact therewith at a constant distance therefrom. The mounting of the magnetic by-pass. 40 may be similar to that of the mounting of coils. 2|, an additional carriage 22', similar to carriage 22 and similarly mounted on carriage ll, being provided therefor. The result of positioning the magnetic conductor by-pass I close to the rail has been found to be a multiplication of the lines of forcethreading through the magneticcircuit between the rail surface and the by-pass l and concentrating a greater number of lines offlux in the rail surface. This concentration of flux has been found to be sumcient to overcome the. local magnetic field which may be set up when a current brush loses contact with the rail or by a dirt spot or by a surface defect. In this manner the local magnetic polesmay be readily eliminated so that the induction coils 20 pickup only internal defects.

In a modified form of the invention, the by-pass ll, instead of being merely. a m'agnetizable member such as a steel block, may be a permanent magnet, or it may be an electromagnet III, as

' shown in Fig. 2.

Still another modification of my invention is disclosed in Fig. 3. In this form there is intercentrated in the plate 40" posed between the coils 20 and the rail surface a magnetizable member 40 which may take the form of a thin plate. The local magnetic field set up by surface defects such as the defect D in Fig. 3, is a permanent magnetic field with a fixed number of lines of flux, and said flux is by-passed by plate III" to eliminate the effect of the local fiux upon the coil 20 in the same manner as the magnetizable member 40. The plate 40 has no effect upon the fiux surrounding the rail due to the current passing through the rail except that morelines of flux are produced in. the field surrounding the rail, theadditional lines being con- To compensate for this additional flux, the coil is moved further away from the rail surface than in the case where plate 40" is not employed.

In accordance with the provisions of the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrativeand that the invention can be carried out by other equivalent means. Also, while it is designed to use the various features and elements in the combination and relations described,-some of these, may be alteredand others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In arail flaw detector mechanism, means for energizing the rail with flux, means responsive to variations in flux, and a magnetic conductor p0- sitioned adjacent the rail and in advance of said responsive means. 2. In a rail flaw detector mechanism, means for energizing the rail with flux, means responsive to variations in flux, and a magnet positioned adjacent the rail and in advance of said responsive means. a

3. In a rail fiaw detector mechanism, means for passing current through the rail to establish an electromagnetic field surrounding the same, said means including brushes for leading the current into and out of theraiL'means responsive to variations in said field, and a magnetic conductor positioned adjacent the rail between the lead-in brushes and said responsive means.

4. In a rail fiaw detector mechanism, means for passing current through the rail to establish an electromagnetic field surrounding the same, 

